More than 1 million children in the United States sustain traumatic brain injury each year. Approximately 90% of pediatric brain injuries are described as mild, yet mild traumatic brain injury(MTBI) research is plagued by problems of classification, measurement,and generalizability. This prospective, longitudinal study wil lseek to define pediatric MTBI according to empirically supportable criteria, measure cognitive and psychological sequelae on multiple occasions, and account for the contribution of premorbid characteristics to the symptoms experienced by children postinjury. Fifty children ages 10-17with MTBI, treated in the emergency department(ED) but not hospitalized, will be recruited. MTBI will be defined by blunt trauma or acceleration deceleration injury to the head followed by any combination of brief loss of consciousness(<30 min.), brief post-traumatic amnesia (<24 hours),alteration in mental state at the time of the accident, and neurological deficits that may be transient. Glasgow Coma Scale scores will be 13-15 with no intracranial pathology on any neuroimaging studies. Fifty control children with comparably severe injuries not involving the head will be recruited in the ED. Relevant historical and demographic information will be obtained. Pre-injury psychological, behavioral, and executive functioning will be assessed via parent checklists. Neurocognitive functioning wil lbe measured with instruments known to be sensitive to brain injury. Post-concussion symptoms(PCS) wil lbe assessed via a questionnaire.The assessments will occur in the ED, one week later,and one month thereafter.The MTBI group is expected to demonstrate more PCS and neurocognitive deficits than controls immediately post-injury and at the one-week follow-up point.Consideringpriorfindings, it is not clear whether the MTBI group will have more PCS and neurocognitive deficits 4-5 weeks post-injury. This study will contribute to the consistent definition of MTBI in children and set the stage for further investigations of the long-term consequences of head injury in children.